Nerve ablation devices and related methods of use

ABSTRACT

An ablation device is provided for forming one or more lesions on a wall of an artery, such as a renal artery. The device can include an elongate shaft having a proximal end and a distal end. The device may also include a handle disposed at the proximal end, a distal tip including an electrode disposed at the distal end, and one or a plurality of independently expandable splines proximate the distal end.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. § 119(e) to U.S. Provisional Application No. 61/794,020, filed Mar. 15, 2013, the entire disclosure of which is herein incorporated by reference.

FIELD

Embodiments of the disclosure are generally directed to devices and methods for ablating target tissue within a body vessel. In particular, exemplary embodiments are directed to devices and methods for ablating tissue on a wall of the renal artery, such as to perform renal denervation.

BACKGROUND

Certain treatments may call for the temporary or permanent interruption or modification of select nerve function. One exemplary treatment is renal nerve ablation, which is sometimes used to treat conditions related to congestive heart failure or hypertension. The kidneys produce a sympathetic response to congestive heart failure, which, among other effects, increases the undesired retention of water and/or sodium. Ablating some of the nerves running to the kidneys may reduce or eliminate this sympathetic function, which may provide a corresponding reduction in the associated undesired symptoms.

Many nerves (and nervous tissue such as brain tissue), including renal nerves, run along the walls of or in close proximity to blood vessels and thus can be accessed intravascularly through the walls of the blood vessels. In some instances, it may be desirable to ablate perivascular nerves and/or tissue using ultrasonic energy. In other instances, the perivascular nerves may be ablated by other means including application of thermal, radiofrequency, laser, microwave, and other related energy sources to the target region.

Conventionally known devices include an ablation catheter having a single electrode at the distal tip, used to deliver radiofrequency (RF) energy, for example, to the target tissue. Sometimes, it is difficult to position the electrode parallel to the vessel wall to obtain an efficient lesion pattern because the ablation catheter may not be controlled to point at the desired locations accurately. Additionally, correct positioning of the electrode may require deflection and/or torquing of the ablation device to place the electrode adjacent a target location within the blood vessel. It is noted that deflection and/or torquing of such ablation devices may include a variety of challenges, for example, potential damage of vessel walls, coagulation of surrounding blood, fouling of the electrode, and so forth.

SUMMARY

The disclosure is directed to several alternative designs, materials and methods of manufacturing medical device structures and assemblies for performing nerve ablation and methods for performing nerve ablation.

Accordingly, one illustrative embodiment is an ablation device. The device includes an elongate shaft having a proximal end region and a distal end region. The device also include a handle disposed adjacent to the proximal end, a distal tip including an electrode disposed at the distal end, and a plurality of independently expandable splines adjacent to the distal end.

Another illustrative embodiment is a method of performing nerve ablation. The method can include insertion of an ablation device into a vessel. The ablation device can include an elongate shaft having a proximal end region and a distal end region, a handle disposed adjacent to the proximal end region, a distal tip including an electrode disposed at a distal end and a plurality of independently expandable splines adjacent to the distal end region. The plurality of splines may be disposed in a first delivery position. The method can also include deployment of a first spline to contact the electrode to a wall of the vessel at a first location in a second expanded position. The method can further include application of RF energy to create a first lesion, which is followed by retraction of the first spline to the first delivery position. The method further includes withdrawing the elongate shaft to a first distance.

The method may also include deployment of a second spline of the plurality of splines to contact the electrode to the wall of the vessel in the second expanded position at a second location different from the first location. The method can include application of RF energy to create a second lesion, which is followed by retraction of the second spline to the first delivery position. Subsequently, the ablation device can be withdrawn from the vessel.

The above summary of some example embodiments is not intended to describe each disclosed embodiment or every implementation of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration of a right kidney and renal vasculature including a renal artery branching laterally from the abdominal aorta;

FIGS. 2A and 2B illustrate sympathetic innervation of the renal artery;

FIG. 3 illustrates various tissue layers of the wall of the renal artery;

FIGS. 4A-4C illustrate various configurations of a conventional ablation catheter within a vessel;

FIG. 5 illustrates an exemplary renal ablation device in accordance with principles of the present disclosure;

FIG. 6A illustrates a schematic side-view of the renal ablation device of FIG. 5 located within a renal artery;

FIG. 6B illustrates a front view of the renal ablation device shown in FIG. 6A;

FIG. 7A illustrates another schematic side-view of the renal ablation device of FIG. 5 located within a renal artery;

FIG. 7B illustrates a front view of the renal ablation device shown in FIG. 7A;

FIG. 8A illustrates another schematic side-view of the renal ablation device of FIG. 5 located within a renal artery;

FIG. 8B illustrates a front view of the renal ablation device shown in FIG. 8A;

FIG. 9A illustrates another schematic side-view of the renal ablation device of FIG. 5 located within a renal artery;

FIG. 9B illustrates a front view of the renal ablation device shown in FIG. 9A;

FIG. 10A illustrates another schematic side-view of the renal ablation device of FIG. 5, located within a renal artery; and

FIG. 10B illustrates a front view of the renal ablation device shown in FIG. 10A;

While embodiments of the present disclosure are amenable to various modifications and alternative forms, specifics thereof have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit aspects of the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the present disclosure.

DETAILED DESCRIPTION

For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification.

All numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the term “about” may be indicative as including numbers that are rounded to the nearest significant figure.

The recitation of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

Although some suitable dimensions ranges and/or values pertaining to various components, features and/or specifications are disclosed, one of skill in the art, incited by the present disclosure, would understand desired dimensions, ranges and/or values may deviate from those expressly disclosed.

As used in this specification and the appended claims, the singular forms “a”, “an”, and “the” include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term “or” is generally employed in its sense including “and/or” unless the content clearly dictates otherwise.

For purposes of this disclosure, “proximal” refers to the end closer to the device operator during use, and “distal” refers to the end farther from the device operator during use.

The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The detailed description and the drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the invention. The illustrative embodiments depicted are intended only as exemplary. Selected features of any illustrative embodiment may be incorporated into an additional embodiment unless clearly stated to the contrary.

Embodiments of the present disclosure are directed to devices and methods for ablating target tissue within a body vessel. Embodiments of the disclosure are directed to devices and methods for ablating perivascular renal nerves from within the renal artery for the treatment of hypertension, congestive heart failure or other diseases or injuries. Embodiments of the disclosure include expandable structures that support alignment of the electrode (s) along the renal artery wall to deliver renal nerve ablation.

While the devices and methods described herein are discussed relative to renal nerve modulation, it is contemplated that the devices and methods may be used in other locations and/or applications where nerve modulation and/or other tissue modulation including, but not limited to, heating, activation, blocking, disrupting, or ablation are desired, such as, but not limited to: blood vessels, urinary vessels, or in other tissues via trocar and cannula access. For example, the devices and methods described herein can be applied to hyperplastic tissue ablation, tumor ablation, benign prostatic hyperplasia therapy, nerve excitation or blocking or ablation, modulation of muscle activity, hyperthermia or other warming of tissues, etc. In some instances, it may be desirable to ablate perivascular renal nerves with radiofrequency (RF) energy. The term modulation refers to ablation and other techniques that may alter the function of nerves and other tissue such as brain tissue or cardiac tissue.

Obtaining good parallel contact with the artery wall during ablation of perivascular renal nerves may be difficult. If contact is variable, the tissue temperatures may not be well controlled, and an ablative temperature may not be achieved in the target tissue, while temperature in other areas, such as portions of the artery wall, may deviate enough to cause unwanted arterial tissue injury. For ideal anatomy, good parallel electrode to vessel contact can be achieved more easily, but especially with tortuous or diseased vessels, there can be very poor contact to effectively and predictably transfer electrical current from an ablation device to the tissue. There is continued need for devices providing improved vessel wall contact for nerve ablation and other therapies.

Embodiments of the disclosure are directed to devices and methods for multi-site RF ablation of perivascular renal nerves for hypertension and other treatments. According to various embodiments, an ablation device may include an elongate shaft having multiple expandable splines near the distal end. The expandable splines may move between a first delivery position and a second expanded position. An RF electrode is mounted on the distal tip of the elongate shaft. The multiple expandable splines can comprise expandable curved, arcuate, or other structures to place the RF electrodes at a desired target location.

When the elongate shaft is deployed, at least one spline may be expanded to come in contact with the artery wall. Such contact between the artery wall and the splines deflects the electrode to contact the artery wall on an opposite side. In some instances, multiple splines may be expanded to place the RF electrode in good parallel contact with the vessel wall.

The elongate shaft can be advanced and deployed in a renal artery to ablate the renal nerves. Activating an RF electrode or combinations of electrodes by energizing from an external energy source may provide one or more discrete RF ablation regions called lesions. Deployment of the ablation device and/or expandable splines can utilize self-expanding elastic forces, push/pull control structures, external retaining and delivery sheaths, and other linkages and structures. An external delivery sheath can be used to protect and constrain the elongate shaft at the distal end during placement and withdrawal. The elongate shaft can be advanced and deployed in a renal artery to ablate the renal nerves. After positioning the shaft's distal end within the renal artery, the delivery sheath can be retracted. Further, the splines may be expanded in a sequential manner allowing the electrode to contact different sites with the renal artery wall.

A proximal end of each of the splines can be connected to a control handle, which may aid in deployment of the splines to the second expanded position. A distal end of each of the splines can be affixed to the distal end region of the elongate shaft adjacent the distal tip. One or more temperature sensors, such as thermocouples, can be provided at the site of the electrode to measure the temperature at or adjacent to the electrode.

FIG. 1 is an illustration of a right kidney 10 and renal vasculature including a renal artery 12 branching laterally from the abdominal aorta 20. In FIG. 1, only the right kidney 10 is shown for purposes of simplicity of explanation, but reference will be made herein to both right and left kidneys and associated renal vasculature and nervous system structures, all of which are contemplated within the context of the disclosed subject matter. The renal artery 12 is purposefully shown to be disproportionately larger than the right kidney 10 and abdominal aorta 20 in order to facilitate discussion of various features and embodiments of the present disclosure.

The right and left kidneys are supplied with blood from the right and left renal arteries that branch from respective right and left lateral surfaces of the abdominal aorta 20. Each of the right and left renal arteries is directed across the crus of the diaphragm, so as to form nearly a right angle with the abdominal aorta 20. The right and left renal arteries extend generally from the abdominal aorta 20 to respective renal sinuses proximate the hilum 17 of the kidneys, and branch into segmental arteries and then interlobular arteries within the kidney 10. The interlobular arteries radiate outward, penetrating the renal capsule and extending through the renal columns between the renal pyramids. Typically, the kidneys receive about 20% of total cardiac output which, for normal persons, represents about 1200 mL of blood flow through the kidneys per minute.

The primary function of the kidneys is to maintain water and electrolyte balance for the body by controlling the production and concentration of urine. In producing urine, the kidneys excrete wastes such as urea and ammonium. The kidneys also control reabsorption of glucose and amino acids, and are important in the production of hormones including vitamin D, renin and erythropoietin.

An important secondary function of the kidneys is to control metabolic homeostasis of the body. Controlling hemostatic functions include regulating electrolytes, acid-base balance, and blood pressure. For example, the kidneys are responsible for regulating blood volume and pressure by adjusting volume of water lost in the urine and releasing erythropoietin and renin, for example. The kidneys also regulate plasma ion concentrations (e.g., sodium, potassium, chloride ions, and calcium ion levels) by controlling the quantities lost in the urine and the synthesis of calcitrol. Other hemostatic functions controlled by the kidneys include stabilizing blood pH by controlling loss of hydrogen and bicarbonate ions in the urine, conserving valuable nutrients by preventing their excretion, and assisting the liver with detoxification.

Also shown in FIG. 1 is the right suprarenal gland 11, commonly referred to as the right adrenal gland. The suprarenal gland 11 is a star-shaped endocrine gland that rests on top of the kidney 10. The primary function of the suprarenal glands (left and right) is to regulate the stress response of the body through the synthesis of corticosteroids and catecholamines, including cortisol and adrenaline (epinephrine), respectively. Encompassing the kidneys 10, suprarenal glands 11, renal vessels 12, and adjacent perirenal fat is the renal fascia, e.g., Gerota's fascia, (not shown), which is a fascial pouch derived from extraperitoneal connective tissue.

The autonomic nervous system of the body controls involuntary actions of the smooth muscles in blood vessels, the digestive system, heart, and glands. The autonomic nervous system is divided into the sympathetic nervous system and the parasympathetic nervous system. In general terms, the parasympathetic nervous system prepares the body for rest by lowering heart rate, lowering blood pressure, and stimulating digestion. The sympathetic nervous system effectuates the body's fight-or-flight response by increasing heart rate, increasing blood pressure, and increasing metabolism.

In the autonomic nervous system, fibers originating from the central nervous system and extending to the various ganglia are referred to as preganglionic fibers, while those extending from the ganglia to the effector organ are referred to as postganglionic fibers. Activation of the sympathetic nervous system is effected through the release of adrenaline (epinephrine) and to a lesser extent norepinephrine from the suprarenal glands 11. This release of adrenaline is triggered by the neurotransmitter acetylcholine released from preganglionic sympathetic nerves.

The kidneys and ureters (not shown) are innervated by the renal nerves 14. FIGS. 1 and 2A-2B illustrate sympathetic innervation of the renal vasculature, primarily innervation of the renal artery 12. The primary functions of sympathetic innervation of the renal vasculature include regulation of renal blood flow and pressure, stimulation of renin release, and direct stimulation of water and sodium ion reabsorption.

Most of the nerves innervating the renal vasculature are sympathetic postganglionic fibers arising from the superior mesenteric ganglion 26. The renal nerves 14 extend generally axially along the renal arteries 12, enter the kidneys 10 at the hilum 17, follow the branches of the renal arteries 12 within the kidney 10, and extend to individual nephrons. Other renal ganglia, such as the renal ganglia 24, superior mesenteric ganglion 26, the left and right aorticorenal ganglia 22, and celiac ganglia 28 also innervate the renal vasculature. The celiac ganglion 28 is joined by the greater thoracic splanchnic nerve (greater TSN). The aorticorenal ganglia 26 is joined by the lesser thoracic splanchnic nerve (lesser TSN) and innervates the greater part of the renal plexus.

Sympathetic signals to the kidney 10 are communicated via innervated renal vasculature that originates primarily at spinal segments T10-T12 and L1. Parasympathetic signals originate primarily at spinal segments S2-S4 and from the medulla oblongata of the lower brain. Sympathetic nerve traffic travels through the sympathetic trunk ganglia, where some may synapse, while others synapse at the aorticorenal ganglion 22 (via the lesser thoracic splanchnic nerve, i.e., lesser TSN) and the renal ganglion 24 (via the least thoracic splanchnic nerve, i.e., least TSN). The postsynaptic sympathetic signals then travel along nerves 14 of the renal artery 12 to the kidney 10. Presynaptic parasympathetic signals travel to sites near the kidney 10 before they synapse on or near the kidney 10.

With particular reference to FIG. 2A, the renal artery 12, as with most arteries and arterioles, is lined with smooth muscle 34 that controls the diameter of the renal artery lumen 13. Smooth muscle, in general, is an involuntary non-striated muscle found within the media layer of large and small arteries and vein, as well as various organs. The glomeruli of the kidneys, for example, contain a smooth muscle-like cell called the mesangial cell. Smooth muscle is fundamentally different from skeletal muscle and cardiac muscle in terms of structure, function, excitation-contraction coupling, and mechanism of contraction.

Smooth muscle cells can be stimulated to contract or relax by the autonomic nervous system, but can also react on stimuli from neighboring cells and in response to hormones and blood borne electrolytes and agents (e.g., vasodilators or vasoconstrictors). Specialized smooth muscle cells within the afferent arteriole of the juxtaglomerular apparatus of kidney 10, for example, produces renin which activates the angiotension II system.

The renal nerves 14 innervate the smooth muscle 34 of the renal artery wall 15 and extend lengthwise in a generally axial or longitudinal manner along the renal artery wall 15. The smooth muscle 34 surrounds the renal artery circumferentially, and extends lengthwise in a direction generally transverse to the longitudinal orientation of the renal nerves 14, as is depicted in FIG. 2B.

The smooth muscle 34 of the renal artery 12 is under involuntary control of the autonomic nervous system. An increase in sympathetic activity, for example, tends to contract the smooth muscle 34, which reduces the diameter of the renal artery lumen 13 and decreases blood perfusion. A decrease in sympathetic activity tends to cause the smooth muscle 34 to relax, resulting in vessel dilation and an increase in the renal artery lumen diameter and blood perfusion. Conversely, increased parasympathetic activity tends to relax the smooth muscle 34, while decreased parasympathetic activity tends to cause smooth muscle contraction.

FIG. 3 shows a segment of a longitudinal cross-section through a renal artery, and illustrates various tissue layers of the wall 15 of the renal artery 12. The innermost layer of the renal artery 12 is the endothelium 30, which is the innermost layer of the intima 32 and is supported by an internal elastic membrane. The endothelium 30 is a single layer of cells that contacts the blood flowing though the vessel lumen 13. Endothelium cells are typically polygonal, oval, or fusiform, and have very distinct round or oval nuclei. Cells of the endothelium 30 are involved in several vascular functions, including control of blood pressure by way of vasoconstriction and vasodilation, blood clotting, and acting as a barrier layer between contents within the lumen 13 and surrounding tissue, such as the membrane of the intima 32 separating the intima 32 from the media 34, and the adventitia 36. The membrane or maceration of the intima 32 is a fine, transparent, colorless structure which is highly elastic, and commonly has a longitudinal corrugated pattern.

Adjacent the intima 32 is the media 33, which is the middle layer of the renal artery 12. The media is made up of smooth muscle 34 and elastic tissue. The media 33 can be readily identified by its color and by the transverse arrangement of its fibers. More particularly, the media 33 consists principally of bundles of smooth muscle fibers 34 arranged in a thin plate-like manner or lamellae and disposed circularly around the arterial wall 15. The outermost layer of the renal artery wall 15 is the adventitia 36, which is made up of connective tissue. The adventitia 36 includes fibroblast cells 38 that play an important role in wound healing.

A perivascular region 37 is shown adjacent and peripheral to the adventitia 36 of the renal artery wall 15. A renal nerve 14 is shown proximate the adventitia 36 and passing through a portion of the perivascular region 37. The renal nerve 14 is shown extending substantially longitudinally along the outer wall 15 of the renal artery 12. The main trunk of the renal nerves 14 generally lies in or on the adventitia 36 of the renal artery 12, often passing through the perivascular region 37, with certain branches coursing into the media 33 to enervate the renal artery smooth muscle 34.

Embodiments of the disclosure may be implemented to provide varying degrees of denervation therapy to innervated renal vasculature. For example, embodiments of the disclosure may provide for control of the extent and relative permanency of renal nerve impulse transmission interruption achieved by denervation therapy delivered using a treatment device of the disclosure. The extent and relative permanency of renal nerve injury may be tailored to achieve a desired reduction in sympathetic nerve activity (including a partial or complete block) and to achieve a desired degree of permanency (including temporary or irreversible injury).

As discussed previously, conventionally known devices may include deflection and/or torqueing of ablation devices to place the electrode adjacent a target location within the blood vessel. It is noted, however, that deflection and/or torqueing of the ablation devices may include a variety of challenges. Examples of such challenges are illustrated in FIGS. 4A-4C, which will be discussed now.

FIG. 4A illustrates an ablation catheter 400 disposed within a vessel having a vessel wall 402 and a vessel lumen 406. The catheter includes a shaft member 408 having an electrode 410 disposed at its distal tip. The shaft member 408 may be introduced within the vessel lumen 406 using an introduction sheath 404, which can be retracted once the member 408 is positioned inside the vessel. Further, the catheter 400 may include a control mechanism (not shown) disposed at a proximal end (not shown) of the shaft member 408. The proximal end may be configured to remain outside the patient's body. The control mechanism may include a handle, for example, that may be employed to deflect the shaft member 408 such as to align the electrode 410 to a target location. In certain instances, the deflection force may bend the distal tip of the shaft member 408 beyond the desired extent. This may cause the electrode 410 to exert a force on the vessel wall 402, which may then dent the vessel wall 402. As a result, the electrode 410 and/or vessel wall 402 may heat beyond a desired threshold temperature and/or blood coagulation may occur, among other undesirable effects. Furthermore, the lesion creation efficacy and patient safety may be difficult to predict and/or control.

FIG. 4B illustrates another incorrect positioning of the ablation catheter 400′. As shown, the shaft member 408 may be deflected along direction D to position the electrode 410 to rest along the vessel wall 402. In some instances, the shaft member 408 may be difficult to torque and control. In some instances, the electrode 410 may contact the vessel wall 402 at an angle instead of extending parallel to the vessel wall. As a result, the lesion creation efficacy and patient safety may be difficult to predict and/or control.

FIG. 4C illustrates yet another incorrect positioning of the ablation catheter 400″ within a vessel. In this instance, the electrode 410 may not be in contact with the vessel wall. This may lead to fouling of the electrode and/or blood coagulation, among other undesirable side effects. As a result, the lesion creation efficacy and patient safety may be difficult to predict and/or control.

FIG. 5 illustrates an illustrative renal ablation device 500 made in accordance with principles of the present disclosure. As shown, the device 500 includes an elongate shaft 502 having a proximal end region 501 and a distal end region 503. The elongate shaft 502 may be configured to enter within a body cavity such as a blood vessel within a patient's body. To this end, the distal end region 503 of the elongate shaft 502 can be introduced within the patient's body, while allowing the proximal end region 501 to remain outside the patient's body. The device 500 may further include a handle 514 operably connected to the proximal end region 501 of the elongate shaft 502, a sensor 508 disposed adjacent to a distal tip 505 of the elongate shaft 502, and multiple expandable splines 504 a, 504 b, 504 c (collectively 504) located adjacent to the distal end region 503 of the elongate shaft 502. The expandable splines 504 may extend generally parallel to a longitudinal axis of the elongate shaft 502 when in an unexpanded configuration, although this is not required. The expandable splines may be attached to the handle 514 at their proximal ends (not explicitly shown) and to the distal tip 505 at their distal ends (not explicitly shown). Each component of the device 500, as discussed above, along with other components will now be described in greater detail.

The elongate shaft 502 may have a long, thin, flexible tubular configuration. A person skilled in the art will appreciate that other suitable configurations such as, but not limited to, rectangular, oval, or irregular shapes may also be contemplated. Further, the elongate shaft 502 may have a cross-sectional configuration adapted to be received in a desired vessel, such as a renal artery. For instance, the elongate shaft 502 may be specially sized and configured to accommodate passage through the intravascular path, which leads from a percutaneous access site in, for example, the femoral, brachial, or radial artery, to a targeted treatment site, for example, within a renal artery.

It is contemplated that the stiffness of the elongate shaft 502 may be modified to form an ablation device 500 for use in various vessel diameters. To this end, the material used for manufacturing the elongate shaft 502 may include any suitable biocompatible material such as, but not limited to, polymers, metals, alloys, shape memory alloys, either in combination or alone. In addition to the stiffness requirement, the material employed elongate shaft 502 can also exhibit sufficient flexibility to maneuver through tortuous and/or stenotic lumens.

Although not shown, the elongate shaft 502 may include one or more lumens extending between the proximal end 501 and the distal end 503. For example, the elongate shaft 502 may include a guidewire lumen and/or one or more auxiliary lumens. The guidewire lumen may extend the entire length of the elongate shaft 502 such as in an over-the-wire catheter or may extend only along a distal portion of the elongate shaft 502 such as in a single operator exchange (SOE) catheter. The lumens may have a variety of configurations and/or arrangements. The lumens may be configured in any suitable way such as those ways commonly used for medical device. These examples are not intended to be limiting, but rather examples of some optional configurations.

Further, the elongate shaft 502 includes multiple slots 510 a, 510 b, and 510 c (collectively 510), which are formed on the outer surface 512 of the elongate shaft 502. As shown, the slots 510 may be formed parallel to the longitudinal length of the elongate shaft 502, while extending around the circumference of the elongate shaft 502. While FIG. 5 illustrates three slots 510, it is contemplated that the elongate shaft 502 may include as many slots 510 as desired for a particular application. For example the elongate shaft 502 may include one, two, four, five, six, or more slots 510. It is further contemplated that the slots 510 may be sized and shaped such that the expandable splines 504 may pass through the slots 510.

As described above, the device 500 can further include multiple expandable splines 504. While three expandable splines 504 are illustrated, it is contemplated that the device 500 may include any number of expandable splines 504 desired, but not limited to, one, two, four, five six, or more. In some embodiments, the expandable splines 504 may have a circular cross-sectional shape. However, this is not required. It is contemplated that the expandable splines 504 may have any cross-sectional shape desired, such as, but not limited to, square, rectangular, ovoid, polygonal, etc. In the illustrated embodiment, the expandable splines 504 may be configured to transition between a first delivery position and a second expanded position. In some embodiments, when in the first delivery position, the expandable splines 504 may be oriented approximately equidistant from a central longitudinal axis of the elongate shaft 502, however this is not required. In some embodiments, the splines 504 may be spaced equidistant from one another. However, this is not required. It is contemplated that the splines 504 may be arranged in any manner desired. As shown in FIG. 5, the expandable splines 504 a and 504 b are depicted in the second expanded position, whereas the expandable spline 504 c resting within slot 510 c correspond the first delivery position. It should be noted that each expandable spline 504 may function independent to each other.

In an embodiment, each expandable spline 504 a, 504 b, and 504 c may rest within their respective slots 510 a, 510 b, and 510 c in the first delivery position. In contrast, in the second expanded state, the splines 504 may extend radially outward from an outer surface of the elongate shaft 502 and out of their respective slots 510 in an arcuate or arch-shaped configuration. The splines 504 may switch to the second expanded position either by a self-expansion mechanism, such as a shape memory material, or by another control mechanism such as push-pull actuation. In the self-expansion mechanism, a portion of each expandable spline 504 may be substantially covered with a sheath, which may allow expansion of the splines 504 when withdrawn. Other control mechanisms may include an actuation mechanism such as handle 514 for manual actuation of the expandable splines 504, which will be discussed below in details. While the splines 504 are described as having an arch-shaped configuration in the expanded position, it is contemplated that the splines 504 may be configured to have different shapes in the expanded configuration, as desired.

The expandable splines 504 may be made from any suitable flexible biocompatible material. Examples may include metals, alloys, polymers, composites, or the like. In an example, the expandable splines 504 are made from a shape memory alloy such as nitinol (NiTi alloy), which may provide super elasticity to the expandable splines 504. Although the material employed should have enough flexibility to form the arch-shaped configuration, it should also have sufficient rigidity to deflect the elongate shaft 502 when in contact with a vessel wall thus allowing the electrode 506 to contact an opposing vessel wall to form one or more lesions. The splines 504 may also be covered with a suitable biocompatible insulation material. Examples may include polymers, composites, or the like. The insulation may prevent or reduce electric conduction between the splines 504 and the vessel wall and/or blood.

The handle 514 may be located at or adjacent to the proximal end region 501, while being operably coupled to the elongate shaft 502. In some embodiments, the handle 514 may be configured to control the distal end region 503 of the elongate shaft 502 and, more specifically, to control the actuation of the expandable splines 504. To accomplish this, the handle 514 may include one or more control elements such as control elements 516 a, 516 b, and 516 c (collectively referred to hereinafter as control elements 516). Each control element 516 a, 516 b, and 516 c may include a button-shaped structure (or other suitably shape structure) that is configured to slide within a slot 518 a, 518 b, and 518 c (collectively 518) in the handle 514. The slots 518 may be sized and shaped to facilitate proximal and distal movement of the control elements 516. In some instances, the control elements 516 may be coupled to the expandable splines 504 such that actuation of the control elements 516 results in a corresponding movement of the expandable splines 504. As shown, an operator may slide the control elements 516 a and 516 b distally in the directions D_(a) and D_(b), respectively, to control the arching of the splines 504 a and 504 b. To this end, control element 516 c is in resting position that enables the spline 504 c to rest within its slot 510 c. In some embodiments, the operator may be able to control how far the splines 504 expand by limiting the distal movement of the control elements 516. For example, control element 516 a and control element 516 b may be slid to a first and a second position, respectively, which enables expansion of the splines 504 a and 504 b to a first and a second expanded position, respectively. Therefore, sliding of each control element 516 may control the expansion of one spline 504. While the control elements 516 have been described as expanding the splines 504 upon distal actuation of the control elements 516, it is contemplated the reverse configuration may also be used and proximal actuation of the control elements 516 will result in the expansion of the splines 504. In some instances, the control elements 516 may include features to allow the splines 504 to be adjusted one or more discrete steps or intervals. In other instances, the control elements 516 may allow the expandable splines 504 to be infinitely adjustable.

Although a slider-based handle is employed or shown to actuate the splines 504, a variety of different mechanisms may be used to actuate the expandable splines 504. For example, the handle 514 may be mechanical or electronic, with varying means of actuation—servo motors, springs, rotary/gear-based, and so forth. In some instances, a push-pull mechanism different from the slider mechanism described above may be used to switch the expandable splines 504 to their second expanded state, although the two mechanisms may be provided on the handle 514 located at the proximal end of the elongate shaft 502. According to some other embodiment, a push-pull mechanism may be provided at a proximal end (not shown) of a delivery sheath, such as sheath 606 shown in FIG. 6A. In such instances, once the delivery sheath encompassing the device 500 reaches a target location within the vessel, the delivery sheath may be pulled to deploy the device 500, or selectively pulled to actuate individual expandable splines 504. Those skilled in the art will appreciate that any suitable actuation mechanism may be employed, which may be located at any suitable to accomplish the desired functions. In addition, while not shown explicitly, the handle 514 may also include one or more ports for introducing any suitable diagnostic and/or treatment devices.

The ablation device 500 may further include an electrode 506 disposed adjacent the distal tip 505 of the elongate shaft 502, which may be employed to ablate the renal nerves. In some embodiments, the electrode 506 may employ radiofrequency energy to ablate the tissue and/or renal nerves. The RF electrode 36 may be made from a suitably conductive metal such as platinum gold, stainless steel, cobalt alloys, or other non-oxidizing materials. While the electrode 506 is described as radiofrequency electrode, it is contemplated that other methods and devices for raising the temperature of the nerves may be used such as, but not limited to, ultrasound, microwave, or other acoustic, optical, electrical current, direct contact heating, or other heating. While not explicitly shown, the electrode 506 may be connected to an energy source or a power and control unit configured through one or more electrical conductors. In some instances, the power and control unit may be a source of RF energy. Furthermore, while not explicitly shown, in some embodiments, the ablation device may include more than one electrode 506.

Further, in some embodiments, a sensor 508 may be disposed within the electrode 506. In some instances, the sensor 508 may include a temperature sensor such as a thermocouple. However, other suitable sensors such as an impedance sensor may also be employed. The sensor 508 may provide feedback, such as the temperature or impedance measurements, to the operator and/or a control unit for monitoring the ablation procedure. For example, the feedback may be indicative of good electrode 506 to vessel contact and/or lesion size. This may facilitate the proper alignment of the electrode 506 with the target tissue and also avoids over heating of the tissue during a renal denervation procedure. In one embodiment, the heat generated at the electrode 506 is measured by the sensor 508, which may help identify if there is suitable contact with the tissue being ablated. For example, a tip suspended in the blood (i.e., not in contact with the vessel wall, like in FIG. 4C) may not exhibit a significant rise in temperature. In addition, electrode 506 that dents the vessel wall resulting from the forced contact with wall (like in FIG. 4A) may heat beyond a desired threshold temperature, indicating an incorrect positioning. For example only, a temperature reading, after a predetermined time period, of 40 degrees C. may indicate contact with the tissue, while 60 degrees C. may indicate the desired contact with the tissue.

As alluded to above, the device 500 may also detect the impedance level while delivering RF energy to the tissue. For instance, an electrode 506 suspended in the blood may exhibit a different impedance level than the electrode 506 having contact with tissue. The impedance can be measured using any conventionally known devices.

Other suitable ways of detecting the desired placement of electrode 506 with the vessel wall may include, but not limited to, imaging methods such as X-Ray, fluoroscopy, and so forth. According to an example, a radiopaque marker may be used to identify the location of the electrode 506 within the vessel. These are just examples and are not limiting the scope of present disclosure.

Turning now to FIG. 6A, a schematic side-view of the renal ablation device 500 is illustrated. The device 500 is located inside a renal artery 600 for creating one or more lesions. More specifically, the device 500 can be located within a lumen 604 of the renal artery 600. Here, the device 500 is present in the first delivery position such the multiple expandable splines 504 are resting within the slots 510 made through the outer surface 512 of the elongate shaft 502. As shown in FIG. 6A, the expandable spline 504 c is flush with an outer surface of the elongate shaft 502 located within the a lumen of the elongate shaft 502 in slot 510 c.

In the illustrated embodiment, the device 500 may be introduced within the artery 600 using a device such as a delivery sheath 606. As shown, the renal ablation device 500 may be slidably disposed within a lumen 608 of the delivery sheath 606. The dimensions of the delivery sheath 606 should be sufficient to carry the device 500 inside the lumen 608 while being navigated through the artery 600. An appropriate actuation mechanism may be provided at the proximal end of the elongate shaft 502. The actuation mechanism may help in deployment the elongate shaft 502 at the target location, while exposing the expandable splines 504 and the electrode 506 to the surrounding vessel.

In the present embodiment, materials used to manufacture the delivery sheath 606 may include a rigid and/or a flexible material either in combination or alone. Additionally, exemplary materials may include metals, polymers, alloys, or composite, either in combination or alone. In an example, an appropriate material to constitute the delivery sheath 606 may include a flexible polymer. Other suitable material may also be contemplated without departing from the scope and spirit of the disclosure.

FIG. 6B illustrates a cross-sectional view of the device 500 shown in FIG. 6A. The cross-section is taken along the vertical plane 6A-6A′. As shown, the electrode 506 may be located within the lumen 604 of the artery 600 while being concentric (although the electrode 506 may not be in the exact center of the lumen 604) to the renal artery 600. It should be noted that the location of electrode may not be suitable for creating any lesion; however, the view is depicted for clear illustration purposes. As shown, the electrode 506 may float within the lumen 604 and is surrounded by the blood flow.

Referring to FIG. 7A, another schematic side-view of the renal ablation device 500 is illustrated. In contrast to the embodiment discussed in FIG. 6A, here, one of the spline 504 a is arranged to be in the second expanded position. The spline 504 a, as shown, may take on an arch-shaped configuration such as to contact the artery wall 602 at a point A. Once the contact between spline 504 a and the artery wall 602 is made, further expansion of the spline 504 a (for example, using the handle 514) may deflect the elongate shaft 502. Such deflection may bias the electrode 506 to contact the artery wall 602 in direction generally opposite to the spline 504 a.

As discussed previously, the delivery sheath 606 is employed to introduce the elongate shaft 502 within the renal artery 600. Once the electrode 506 is positioned at the target location adjacent the artery wall 602, RF energy may be supplied to the electrode 506. As the energy is radiated from the electrode 506, the electrode 506 may heat up. While not shown explicitly, the device 500, along with the temperature sensor 508, may also include a cooling mechanism to regulate the temperature of the electrode 506. Such mechanisms may include any suitable cooling method such as infusion of fluid around the electrode, which circulates the blood around the electrode 506 that may result in lowering the temperature around the electrode 506.

Although single spline 504 a is expanded in the present embodiment, it should be noted that two or more splines 504 may be expanded simultaneously such as to place the electrode 506 at a desired target location. To this end, two or more splines 504 may be expanded either simultaneously or sequentially. In addition, the amount of energy delivered to the electrode 506 may be determined by the desired treatment as well as the measured temperature provided by the sensor 508.

FIG. 7B illustrates a cross-sectional view of the device 500 shown in FIG. 7A. The cross-section is taken along the plane 7A-7A′. As shown, the electrode 506 is located adjacent the artery wall 602, whereas the spline 504 a touches the artery wall at a vertically opposite end. In such an arrangement, the alignment of the electrode 506 may be adjusted by manipulating the expansion of the spline 504 a.

Turning now to FIG. 8A, yet another schematic side-view of the renal ablation device 500 is illustrated. In contrast to the embodiment discussed above in FIGS. 6A-7B, here, another spline 504 b is configured to be in the second expanded position, as discussed previously. The spline 504 b may take on an arch-shaped configuration such as to contact the artery wall 602 at a point B. Once the contact between spline 504 b and the artery wall 602 is made, further expansion of the spline 504 b (for example, using the handle 514) may deflect the elongate shaft 502 towards an artery wall 602. Such deflection may bias the electrode 506 to contact the artery wall 602 in a direction generally opposite to the spline 504 b. It should be noted that the spline 506 b may contact the artery wall at a point B, which is generally opposite to the point A. For example, the spline 506 b contacts the artery wall 602 at an angle of approximately 180 degrees to the point A.

The delivery sheath 606 is employed to introduce the elongate shaft 502 within the renal artery 600. Once the electrode 506 is positioned at the target location adjacent the artery wall 602, RF energy may be supplied to the electrode 506. As the energy is radiated from the electrode 506, the electrode 506 may heat up. While not shown explicitly, the device 500, along with the temperature sensor 508, may also include a cooling mechanism to regulate the temperature of the electrode 506. Such mechanisms may include any suitable cooling method such as infusion of fluid around the electrode, which circulates the blood around the electrode 506 that may result in lowering the temperature around the electrode 506.

FIG. 8B illustrates a cross-sectional view of the device 500 shown in FIG. 8A. The cross-section is taken along the plane 8A-8A′. As shown, the electrode 506 is located adjacent the artery wall 602, and the spline 504 b touches the artery wall 602 at an approximately vertically opposite end. In such an arrangement, the alignment of the electrode 506 may be adjusted by manipulating the expansion of the spline 504 b.

FIGS. 9A-9B illustrate positioning of the electrode 506 adjacent the artery wall 602 using spline 504 c. Here, as distal end region 503 of the elongate shaft 502 is situated within the artery lumen 604 adjacent the target location, the delivery sheath is retracted. Further, the control element 516 c (as shown in FIG. 5) may be slid toward the elongate shaft 502, which expands the spline 506 c to its second position. In such position, the spline 506 c may contact the artery wall at a point, which deflects the elongate shaft 502 facilitating the electrode 506 to contact the artery wall 602 at an opposite side, as shown in FIG. 9B.

For the purpose of illustration, the spline 506 c is depicted to form the arch-shaped configuration, however, it should be noted that the spline 506 c is arched in transverse plane of the elongate shaft 502. To this end, the spline 506 c may be assumed to contact the artery wall at a point (not shown) at an angle of approximately 90 degrees to the contact A that is made by spline 504 a (as discussed in FIGS. 6A-6B).

FIGS. 10A-10B illustrate positioning of the electrode 506 adjacent the artery wall 602 using a fourth spline 504 d. Here, as distal end 503 of the elongate shaft 502 is situated within the artery lumen 604 adjacent the target location, the delivery sheath is retracted. Further, a fourth control element (not explicitly shown) may be slid toward the elongate shaft 502, which expands the spline 506 d to its second position. In such position, the spline 506 d may contact the artery wall at a point, which deflects the elongate shaft 502 facilitating the electrode 506 to contact the artery wall 602 at an opposite side, as shown in FIG. 10B.

For the purpose of illustration, the spline 506 d is depicted to form the arch-shaped configuration, however, it should be noted that the spline 506 d is arched in transverse plane of the elongate shaft 502. To this end, the spline 506 d may be assumed to contact the artery wall at a point (not shown) at an angle of 90 degrees to the contact A that is made by spline 504 a (as discussed in FIGS. 6A-6B). In addition, the angle between the splines 506 c and 506 d, while each contacts with the artery wall 602 in its second expanded state, may be approximately 180 degrees.

According to a method of performing renal ablation, the device 500 may be inserted into the renal artery 600 and advanced to the desired treatment region. Subsequently, a first spline, such as the spline 504 a, may be deployed to contact the electrode 506 to the renal artery wall 602 at a first location such as point A, as shown in FIG. 6A. Further, the RF energy may be applied to create a first lesion, which is followed by retraction of the first spline 504 a to the first delivery position.

Further, a second spline such as spline 504 b may be deployed to contact the wall 602 at a second location such as point B, as shown in 6B. Next, the RF energy may be applied to create a second lesion, which is followed by retraction of the second spline 504 b to the first delivery position. Here, the deployment of one or more splines 504 to the second expanded position biases the electrode 506 toward the wall 602 of the renal artery 600 in a direction opposite the deployed spline 504. This way the sequential deployment of splines 504 may form multiple lesions on the wall 602. This may be repeated as many times as necessary to form the desired number and/or size of lesions. In some instances, the elongate shaft 502 may be longitudinally displaced in the artery 600 after the formation of a lesion. This may result in longitudinally spaced lesions. It is contemplated that the lesions may be formed along a single side of the artery 600 or the lesions may be spaced about the circumference of the artery 600. In some instances, the elongate shaft 502 may be longitudinally displaced after each lesion, and each spline 504 may be actuated sequentially to form lesions in a generally helical pattern. It is further contemplated that the temperature response and/or the impedance level may be checked prior to actuating a different spine 504 or relocating the elongate shaft 502.

Various embodiments disclosed herein are generally described in the context of ablation of perivascular renal nerves for control of hypertension. It is understood, however, that embodiments of the disclosure have applicability in other contexts, such as performing ablation from within other vessels of the body, including other arteries, veins, and vasculature (e.g., cardiac and urinary vasculature and vessels), and other tissues of the body, including various organs.

It is to be understood that even though numerous characteristics of various embodiments have been set forth in the foregoing description, together with details of the structure and function of various embodiments, this detailed description is illustrative only, and changes may be made in detail, especially in matters of structure and arrangements of parts illustrated by the various embodiments to the full extent indicated by the broad general meaning of the terms in which the appended claims are expressed. 

What is claimed is:
 1. An ablation device for performing nerve ablation in a vessel wall, comprising: an elongate shaft having a proximal end region and a distal end region; a handle disposed adjacent to the proximal end region; a distal tip including a single electrode, which is the only electrode in the ablation device, disposed at a distal end of the elongate shaft; and a plurality of expandable splines adjacent to the distal end region and positioned proximal to the single electrode; wherein each of the plurality of expandable splines is independently actuatable between a first contracted position and a second expanded position that extends radially outward to a variable distance from the outer surface of the elongate shaft; and wherein the ablation device is configured such that independent actuation of each of the plurality of expandable splines to the second expanded position against a wall of a vessel biases the single electrode in a direction that is generally radially opposite to the actuated spline.
 2. The ablation device of claim 1, wherein in the first contracted position, each of the plurality of expandable splines is flush with or contained within an outer surface of the elongate shaft.
 3. The ablation device of claim 1, wherein in the second expanded position, the plurality of expandable splines form an arcuate shape.
 4. The ablation device of claim 1, wherein the plurality of expandable splines includes at least four expandable splines.
 5. The ablation device of claim 1, wherein each of the plurality of expandable splines is oriented generally equidistant about a central longitudinal axis of the elongate shaft.
 6. The ablation device of claim 1, wherein each of the plurality of expandable splines includes an insulative covering.
 7. The ablation device of claim 1, wherein the handle includes a plurality of control elements configured to actuate the plurality of expandable splines.
 8. The ablation device of claim 1, wherein a distal end of each of the plurality of expandable splines is attached to the distal end of the elongate shaft and a proximal end of each of the plurality of expandable splines is attached to a control element.
 9. The ablation device of claim 1, further including a temperature sensor disposed within the distal tip.
 10. An ablation device for performing nerve ablation in a vessel wall comprising: an elongate shaft having a proximal end region and a distal end region; a handle disposed adjacent to the proximal end region; a distal tip including a single electrode, which is the only electrode in the ablation device, disposed at a distal end of the elongate shaft; and a plurality of splines adjacent to the distal end region and positioned proximal to the single electrode, wherein each one of the plurality of splines is independently actuatable between a first contracted position, and a second expanded position that extends radially outward to a variable distance from the outer surface of the elongate shaft; wherein the plurality of splines includes at least three independently actuatable splines; and wherein the ablation device is configured such that independent actuation of each of the plurality of splines to the second radially expanded position against a wall of a vessel biases the single electrode in a direction that is generally radially opposite to the actuated spline.
 11. The ablation device of claim 10, wherein the handle includes a plurality of control elements each configured to independently actuate one of the plurality of splines.
 12. A method of performing nerve ablation, comprising: inserting the ablation device of claim 1 into a vessel; deploying one or more of the plurality of splines to the second expanded position such that the single electrode is brought into contact with a wall of the vessel at a first location; applying RF energy at the first location through the single electrode; retracting the one or more deployed splines to the first contracted position; moving the elongate shaft to a second location; deploying one or more of the plurality of splines to the second expanded position such that the single electrode is brought into contact with a wall of the vessel at the second location; applying RF energy at the second location through the single electrode; retracting the one or more deployed splines to the first contracted position; and withdrawing the ablation device from the vessel.
 13. The method of claim 12, wherein the plurality of splines includes at least four splines.
 14. The method of claim 12, wherein before withdrawing the ablation device, the method further includes: moving the elongate shaft to a third location; deploying one or more of the plurality of splines to the second expanded position such that the single electrode is brought into contact with a wall of the vessel at the third location; applying RF energy at the third location through the single electrode; retracting the one or more deployed splines to the first contracted position; moving the elongate shaft to a forth location; deploying one or more of the plurality of splines to the second expanded position such that the single electrode is brought into contact with a wall of the vessel at the fourth location; applying RF energy at the forth location through the single electrode; and retracting the one or more deployed splines to the first contracted position.
 15. The method of claim 12, wherein deploying one or more of the plurality of splines to the second expanded position biases the single electrode toward the wall of the vessel in a direction generally opposite the direction that the one or more splines are deployed.
 16. An ablation device for performing nerve ablation in a vessel wall, comprising: an elongate shaft having a proximal end region and a distal end region; a handle disposed adjacent to the proximal end region; a distal tip including a single electrode, which is the only electrode in the ablation device, disposed at a distal end of the elongate shaft, the single electrode extending circumferentially around the distal end of the elongate shaft; and a plurality of expandable splines adjacent to the distal end region and positioned proximal to the single electrode; wherein each of the plurality of expandable splines is independently actuatable between a first contracted position, and a second expanded position that extends radially outward to a variable distance from the outer surface of the elongate shaft; wherein the ablation device is configured such that independent actuation of each of the plurality of expandable splines to the second radially expanded position against a wall of a vessel biases the single electrode in a direction that is generally radially opposite to the actuated spline; wherein in the first delivery position, each of the plurality of expandable splines is contained within a slot in an outer surface of the elongate shaft; wherein in the second expanded position, the plurality of expandable splines form an arcuate shape; and wherein the plurality of expandable splines includes at least three expandable splines.
 17. The ablation device of claim 16, wherein each of the plurality of expandable splines comprises an insulative covering.
 18. The ablation device of claim 16, wherein each of the plurality of expandable splines is formed from a polymer.
 19. The ablation device of claim 16, wherein an axial cross-section of each of the plurality of expandable splines is rectangular, circular or ovoid.
 20. The ablation device of claim 16, wherein the handle includes a plurality of control elements configured to actuate the plurality of expandable splines. 